Charlie Day shows new extreme in Pacific Rim'

On “It’s Always Sunny In Philadelphia,” he plays one of the dimmest-witted characters in TV history. Philly bar owner Charlie Kelly is so daft he makes Joey from “Friends” seem like a Rhodes Scholar.

But in “Pacific Rim,” the robots vs. monsters actioner from Guillermo Del Toro (“Hellboy,” “Pan’s Labyrinth”), Day leaves the dumb-and-dumber shtick behind to portray a scientist the actor calls “the smartest man on the planet.”

Day’s alter ego in the movie, Dr. Newton Geiszler, is such a brainiac, in fact, he has to dial down his smartness just so he won’t embarrass everyone else in the room.

“It’s very cool to finally get to play myself,” teases Day. “No, look, I was glad just to play a character who can read and write.”

Offscreen, there is no doubt that Day is a smart guy. He not only created “It’s Always Sunny” with pals Rob McElhenney and Glenn Howerton but he’s also picked his big-screen projects wisely. “Horrible Bosses” was a surprise hit back in 2011 and “Monsters University” took in more than $170 million during its first two weeks, beating “World War Z” and “The Heat,” among other entries.

“It’s nice to be having a monster summer,” says the actor, who plays the spacy scare machine Art alongside Billy Crystal, John Goodman and Helen Mirren.

In “Pacific Rim,” opening Friday, Day and company do battle with a much different brand of monster. The action begins in the aftermath of an invasion of Kaiju, or massive, Godzilla-like creatures who arise from a breach in the ocean floor. To combat the Kaiju, the government develops 700 foot robots called Jaegers which are manned by teams of heroic humans.

But when more and more monsters begin to emerge, a ragtag gang of Jaeger pilots (Charlie Hunnam, Rinko Kikuchi, Max Martini, Rob Kazinsky), military commanders (Idris Elba) and scientists (Day, Burn Gorman) gather together for a last-ditch effort to close up the breach and shut-down the mounting apocalypse.

While Day provides some much-needed comic relief, he also gets sucked into the action and is arguably the dude with the best idea of how to save the world.

“I didn’t want to do the part if it was just me coming in and doing a bunch of knock-knock jokes, and being the random wacky guy in the middle of the movie,” says Day, 37. “I wanted the opportunity to be a big part of the story and then also try and bring levity through my character.”

While Hunnam and Elba get more screen time, it’s Day’s nerdy scientist who undergoes the biggest transformation.

“I like that Newt starts out cocky and arrogant,” says Day. “And then he gets a bit of a beatdown over the course of the movie. You get to see this guy go from pompous to heroic. That was an appealing thing.

“I also saw Newt as this guy who is struggling a bit with a sense of identity. The jocks get all of the credit for stopping these creatures while the brains behind the brawn . So Newt doesn’t want to be a bowtie-wearing scientist. He wants to be a rock star. He’s not that but he does put his life at risk and he does get to fulfill his in a big way.”

Everything about “Pacific Rim” is big. Largely shot in Pinewood Studios in Toronto, the film (which was budgeted at $180 million) used 101 sets, which took up nine massive soundstages. Outdoor locations included Lake Ontario beach and Hearn power plant.

Many of Day’s scenes take place in Hong Kong, where he goes in search of an underground dealer (Ron Perlman) who salvages Kaiju corpses and sells them on the black market. In the midst of Newt’s mission, a Kaiju attacks.

Most of the monsters were added to the film via computer in post-production but Day insists he rarely worked in front of a green screen.

“What’s so great about Guillermo is that he builds these massive, elaborate sets,” notes the actor. “For the Hong Kong sequence, they created four city blocks on soundstages in Toronto.

“There were 500 extras screaming and running and there were people on bicycles and scooters going this way and that. I actually asked Guillermo, ‘aren’t you going to do any of this with green screen?’

“And then he’d explain the technology to me in a way I didn’t understand. But it was great. He’d say, ‘action’ and you’d be in this environment where you’re running and scrambling and getting knocked over while cars are flipping over around you.

“And then you’d have look up for a moment and be terrified. It was easy because you were sufficiently terrified of being trampled.”

Among its other distinctions, “Pacific Rim” might be the wettest movie in Hollywood history. And even though the torrential downpours were simulated inside the studio and the water was heated up to 90 degrees to keep the actors comfortable, the drenchings took their toll on the cast members.

“It was weird because we were shooting in Toronto and it was snowing outside and raining inside,” says Day. “That rain was not in the script. I didn’t see that when I accepted the role.

“But, it actually did help my performance. Details like that make it easier for you to believe you’re really in that environment, and visually, for the audience, it helps breathe life into a movie where elements are animated.”

Del Toro made it up to Day by allowing him a freedom he rarely affords his actors. The filmmaker is infamous, in fact, for the amount of control he exerts on every shot. But he opted to shoot Day with three cameras so the actor could improvise and move around without worrying about hitting marks.

“It helped me make Newt more of an everyman,” says Day. “Guillermo allowed me to give a looseness and some rough edges to the character, and I think that helps relate to him.”

Growing up in Rhode Island, Day was always interested in the arts. The son of music-school teachers, he attended Merrimack College in North Andover, Massachusetts as an art history major before he landed a job with the Williamstown Theatre Festival in 1997.

While performing at one of the Festival’s cabaret nights, he netted an agent and soon began appearing on TV shows like “Third Watch,” “Law & Order” and “Reno 911,” where he and his future wife Mary Elizabeth Ellis played incestuous siblings. Day married Ellis (who is the Waitress on “Sunny”) in 2006 and they had their first child, Russell, in 2011.

Day’s career took a big turn in 2004 when he and his buddies McElhenney and Howerton sold their homemade “Sunny” pilot to F/X. The men wrote, directed, produced and starred in the initial episode for $50. Their tagline: “Seinfeld on crack.”

Nine seasons later, “Sunny” is still going strong. “It’s nice to still be discovering things for these characters to do,” says Day, who promises the show will return for a tenth season. “I still enjoy it. It’s been the most rewarding working experience of my life. So I’m thrilled to be a part of it and we want to keep it going as long as we possibly can.”

After 10 years of playing a Philadelphian — and occasionally hanging out at McElhenney’s real-life Philly bar, Mac’s Tavern — Day is synonymous with the City of Brotherly Love.

“Everyone thinks I’m from Philly because of the show and I hate to disappoint them,” says the actor. “Of course, I’m from Rhode Island but I can see how bummed out people are when they see me in a Red Sox hat.

“What are you going to do? People have fallen in love with this character and he feels real to them. It’s a big compliment, in a way. I’m glad people think Charlie is the real deal.”